Plasma etch tools are one of the more common machines used throughout the wafer fabrication industry. Plasma etch tools are programmed to precisely remove material in a desired area of a wafer. The physical components of a plasma etch tool include a processing chamber, a vacuum pumping system, gas sources, and a radio frequency (RF) power supply.
The plasma etching process occurs in the following generic sequence. Wafers first enter the processing chamber via robotic transfer. The pumping system is activated and proceeds to pull the processing chamber into a desired state of vacuum. Gases are then introduced into the chamber and allowed to mix. A power supply is then activated which creates an RF field using electrodes within the processing chamber. The energized gas mixture then converts to a "plasma" or ionized form and reacts with the wafer surface to begin the etching process.
One result of this dry etch process is the formation of gaseous byproduct compounds that are exhausted from the plasma etch tool processing chamber through the vacuum pumping system. Although most of the compounds exit the processing chamber via the vacuum pumping system, some byproducts also adhere to the walls of the processing chamber. These byproducts eventually result in particle contamination of wafers being processed in the chamber. When in-situ statistical process control monitoring systems detect a process shift due to particle contamination, the plasma etch tool is taken out of service and the vacuum system is vented to atmosphere.
At this time, etch technicians perform a manual chamber clean. Before opening the processing chamber, a cyclic nitrogen purge process is usually applied in the vacuum state. Manual cleaning of etch processing chambers typically uses an industry standard 3% solution of isopropyl alcohol (IPA) and deionized water (DI) to physically wipe down and clean the particle laden chamber walls and ceramics. At the time of opening a purged processing chamber and especially as the IPA/DI cleaning solution comes into contact with the chamber residues, particularly odorous byproducts are formed and emit from the chamber components.
Since wafer fabrication occurs in cleanroom environments, a large amount of air is continuously moved through high efficiency particulate attenuation (HEPA) filters in order to limit particle contamination of the wafers being processed. Because of the large amount of air circulating, odorous byproduct emissions produced during manual plasma etch chamber cleans are frequently transferred throughout the fabrication area. Therefore, not only are etch technicians working on the chamber clean effected by the odors, but so are the operators, engineers and other support people who are working in the immediate and surrounding areas.
Several approaches have been used in the past to address the odor problem that occurs during plasma etch tool chamber cleans.
In one approach, no extra precautions are employed, and the odorous off-gassing is allowed to circulate per normal cleanroom air flow. As a result, technicians involved with a chamber clean minimize the time they are working over the chamber opening, thereby slowing the cleaning process. Operations and other factory personnel working in the immediate area either move to an area where odors are not detectable, or leave the processing area altogether until the fab air exchanges clear the odors. This procedure can contribute to lost production time due to operators being forced to leave their equipment or to factory evacuations if the odors become too intense.
A second approach to handle odorous off-gassing involves running a trunk line from the house acid exhaust system. When a plasma etch chamber clean occurs, the trunk line is placed near the chamber opening or hung over the chamber opening. Neither case is effective in capturing the byproduct off-gassing from the chamber opening. Significant odors are still prevalent.
Another approach used in the past is to exhaust the processing chamber through the vacuum duct of the etch tool. Such a task requires removing components of the vacuum pump system downstream of the plasma etch processing chamber and connecting a flexible acid exhaust duct line. This method typically results in additional equipment downtime required to disassemble tool components, as well as incomplete capture of the odors being created during the chamber cleaning process.
Accordingly, it would be advantageous to have a ventilation fixture and a method of employing same which overcome these and other deficiencies of the prior art.